This invention pertains to input-output devices and, more particularly, to such devices which can connect a central station to a plurality of different remote stations.
Universal controls have many applications. Particularly important applications today concern the control of energy, airconditioning, lighting and processing. Because of the accelerating cost of fuel, it is becoming more and more necessary to practice energy conservation in commercial, industrial and public buildings. This conservation takes place by controlling the lighting, heating, ventilation and air-conditioning in different areas of the building on a purely on-demand basis. To perform this function, there is distributed throughout the building sensors which determine the ambient conditions of the particular zones in the building. Also within the zones there are devices for controlling the lighting in the zone as well as devices for supplying heat and air conditioning. Since the zones are diffused throughout the building, there is generally provided a central control connected by means of wires to the sensors and operable devices in the diffused zones. Heretofore, such systems were custom-made and used a jigsaw puzzle assemblage of devices at the remote terminals. This approach is not only expensive, but is difficult to troubleshoot and monitor.